Water dispersible PU resins containing sulfonate group have been described in many patents, including:
(a) Use of sodium salt of N-(2-aminoethyl)-2-aminoethane sulfonic acid for the chain extender and emulsifier of water-borne PU resins, reported by the Bayer AG of Germany in following patents: PA1 (b) Use of sulfonate of diols as one of the raw materials in preparing water-borne PU resins by the Bayer AG as reported in following patents: PA1 (c) In the Patent PCT/US95/00030, 5-sulfoisophthalic acid monosodium salt is used as raw material to synthesize water-borne PU adhesive with high green PA1 m=2.about.12 PA1 n=1.about.3 PA1 A=K or Na. PA1 tetramethylene diisocyanate PA1 hexamethylene diisocyanate (HDI) PA1 1,4- diisocyanatocyclohexane PA1 4,4'- diisocyanatodicyclohexylmetlhane (H.sub.12 MDI) PA1 isophorone diisocyanate (IPDI) PA1 tetramethylxylylene diisocyanate (TMXDI) PA1 diphenylmethane-4,4'- diisocyanate(MDI) PA1 toluylene diisocyanate (TDI) PA1 xylylene diisocyanate (XDI) PA1 mixture of above diisocyanates PA1 adipic acid PA1 phthalic acid PA1 tetrahydrophthalic acid PA1 hexahydrophthalic acid PA1 ethylene glycol PA1 propylene glycol PA1 butylene glycol PA1 hexamethylene glycol PA1 glycerol PA1 trimethylol propane PA1 diethylene glycol PA1 triethylene glycol PA1 tetraethylene glycol PA1 polytetramethylene glycol( PTMG) PA1 polypropylene glycol(PPG) PA1 polyethylene glycol (PEG) PA1 ethylene diamine PA1 hexamethylene diamine PA1 isophorone diamine PA1 2,4-diaminotoluene PA1 4,4'-diaminodicyclohexylmethane PA1 diethylene triamine PA1 triethylene tetraamine PA1 hydrazine PA1 hydrazine hydrate. PA1 m=2.about.12 PA1 n=1.about.3 PA1 A=K or Na.
Ger. Offen. 2804609 PA2 Ger. Offen. 2900574 PA2 Ger. Offen. DE 3216567 PA2 Ger. Offen. DE 3415290 PA2 Ger. Offen. DE 3603996 PA2 Ger. Offen. DE 3630045 PA2 U.S. Pat. No. 4056564 PA2 U.S. Pat. No. 4108814 PA2 Ger. Offen. 2446440
When water-borne PU adhesive is coated on the substrate as rubber, metals or PVC, water shall be driven off first by heating followed by thermal activation of the adhesive layer to perform bonding. In case the formulation of water-borne PU is not appropriate to cause higher activation temperature and damage the substrate. The method to lower the activation temperature through the use of more solvent, plasticizer or other resin shall lead to significant loss of heat strength.
Besides, in actual use of water-borne PU for adhesive, the operation aspect should be considered to avoid very short tack time in practice. The extension of tack time is an important topic in the use of water-borne PU resin.
In order to improve the activation temperature and tack time during the use of water borne PU for adhesive, this invention introduces the use of ethylene oxide sulfonates in the side chain of water borne PU molecules to form excellent bonding of said water borne PU with improved activation temperature and tack time.
According to the present invention, the structure of diamine sulfonates is shown as following: ##STR1##
in which
In the use of diamine sulfonates of this invention, the acetone process, as described in Ger. Off. 1495745 and 1495247, can be applied, to add acetone to dissolve the pre-polymer after its formation, followed by chain extension with aliphatic diol or diamine with dispersion of water to obtain water borne PU resin with high molecular weight, after completing the reaction, acetone can then be removed by distillation under reduced pressure.
In the synthesis of water-borne PU for adhesive, the raw materials include:
(I) Diisocyanates with the general formula EQU Q(NCO).sub.2 PA0 (II) The molecular weight of polyester polyols is in the range from 400 to 10,000, most preferably from 400 to 4,000, the preparation of these polyester polyols is by condensation of dibasic carboxylic acid with excess dihydric alcohols, the required dibasic acids include PA0 (III) Amine chain extenders having molecular weight between 30 to 440 include: PA0 (IV) Glycol chain extenders having molecular weight between 60.about.400 such as ethylene glycol and butylene glycol are used. PA0 (V) Chain extenders and emulsifyers containing sulfonate with following structure: ##STR2##
in which Q=aliphatic hydrocarbon radical with 4.about.12 carbon
or =cycloaliphatic hydrocarbon radical with 6.about.15 carbon
or =araliphatic hydrocarbon radical with 7.about.15 carbon.
These diisocyanates include
The molar ratio of diisocyanates to polyols (abbreviated as NCO/OH) is from 1.1:1 to 10:1, most preferably, from 1.2:1 to 2.5:1.
The glycols or polyols having molecular weight in the range of 60.about.400 include:
The polyether polyols include:
Other polyols include polycarbonate polyol, polycaprolactone or the mixture of above polyols.
in which
By introducing above sulfonates to the main chain of PU, the amount is for each 100 g of polymer with 5.about.200 milliequivalent of said slfonate for dispersion in water.
The reaction temperature for preparing prepolymer in general is between 5.about.160.degree. C., most preferably between 50.about.120.degree. C. The reaction temperature for chain extension in general is between 20.about.100.degree. C., most preferably between 20.about.80.degree. C. The removal of solvent as acetone in general is by distillation under reduced pressure, the temperature to be controlled between 20.about.100.degree. C., most preferably between 30.about.90.degree. C. The pressure is controlled between 5.about.1100 mbar, most preferably between 10.about.300 mbar.
The water-borne PU resin in this invention has good stability in forming emulsion, to be used as adhesive with better activation temperature and tack time.
The embodiment of this invention is illustrated as following: